The present invention relates generally to a device for the noninvasive measurement of electrical current through a conductor and in particular to a device that may be installed in the field for measuring electrical current with a Hall effect sensor.
Electrical power is typically produced at centralized power production facilities and transferred at high voltages to local substations. The local substations transform the electrical power to a medium or low voltage. The electrical power is subsequently distributed through feeders to local distribution networks. The power is thus delivered to an end customer that consumes the electrical power.
Since the electrical power is often transmitted over long distances, reliability and integrity of the system are major considerations in the design of the transmission system. During transmission of the electrical power, a number of different faults may occur due to events such as vegetation growth and lightening strikes for example. A number of control devices are used within the transmission system such as fuses, transformers, circuit breakers, reclosers and protective relays. These devices help control the flow of electrical power and provide functionality for removing electrical power in the event of an electrical fault.
A protective relay is a type of device that detects undesirable electrical conditions, such as high voltage for example. The protective relay operates in conjunction with a circuit breaker for interrupting the flow of electrical current when the undesired condition is detected. Protective relays have selectable time/current curves that allow the operator to have a fine level of control over the triggering conditions. One type of protective relay uses elaborate electromechanical components, such as but not limited to arrays of induction disks or induction cylinders, shaded-pole magnets, operating and restraint coils, solenoid-type operators, and phase-shifting networks for example, to allow the relay to respond to such conditions as over-current, over-voltage, reverse power flow, over-frequency and under-frequency for example. Protective relays may even be arranged to provide trip functionality for faults up to a certain distance away from a substation but not beyond that point by measuring the apparent impedance.
When a fault occurs, the electromechanical type protective relay provides a signal to the circuit breaker to interrupt the current flow. A mechanical indicator, sometimes referred to as a target flag, is then displayed on the relay to visually indicate the detection of the undesired condition. To restore service, repair personnel need to physically visit the substation where the relays are located and perform an inspection to determine which protective relay operated. Some applications, such as a substation for example, may have many protective relays that cover a wide geographic area. Thus, the process of physically inspecting and identifying the relay may be time consuming and costly.
Accordingly, while existing systems and methods for determining the operation of protective relays are suitable for their intended purposes, there still remains a need for improvements particularly regarding the coupling of sensors with conductors such as those used with electromechanical relays to allow remote detection of electrical characteristics.